JEE Main · 2021 · 20 Jul 2021 · Shift 1 · General Principles and Processes of Isolation of Metals

Fractional distillation refines a metal that is itself volatile while its impurities are not, so the metal distils over and the impurities stay in the still. Zinc boils at about $1180\mathrm{K}$, low enough for the metal to be vaporised and condensed cheaply, and its usual impurities lead and cadmium separate on fractionating the vapour. Iron, copper and nickel all boil above $2800\mathrm{K}$, so distillation is uneconomic for them: nickel is refined through its volatile carbonyl and copper electrolytically. The metal purified economically by fractional distillation is zinc.